Polygon reduction is a term used to describe techniques for reducing the complexity of a polygon mesh while minimizing alterations to attributes of the polygon mesh. Example attributes of a polygon mesh include but are not limited to its general shape, sharpness of features, color variations, etc. A polygon mesh of reduced complexity uses less memory and is faster to display.
A widely used technique for polygon reduction is based on the progressive mesh algorithm described by Hugues Hoppe in “Progressive Meshes,” in Proceedings of SIGGRAPH '96, pages 99-108, August 1996 (“Hoppe”). The algorithm involves iteratively contracting adjacent vertex pairs (or edges between them) into one vertex, which is then positioned to minimize attribute changes. At each iteration, the algorithm chooses the pair that will be contracted with the minimal attribute change. The quantification of this change is called a “cost.” This cost can be computed using various metrics, such as described in “Surface Simplification Using Quadric Error Metrics,” by M. Garland and P. Heckbert in Proceedings of SIGGRAPH '97, pages 209-216 (“Garland”), and in “Fast and Memory Efficient Polygonal Simplification,” by P. Lindstrom and G. Turk, in Proceedings of IEEE Visualization '98, pages 279-286 (“Lindstrom”).